CONFIGURATION-DEPENDENT PROPERTIES OF POLY(DIMETHYLSILOXANE) CHAIN

The intermolecular rotational potential energies for poly(dimethylsiloxane) (PDMS) chains are directly obtained from a priori probability P-alpha beta. Here the differing statistical weight matrices for the Si-O and O-Si bonds are considered in calculating the configuration partition function. In the Bahar's model, as the same statistical weight matrices for the Si-O and O-Si bonds are adopted, there exists a large deviation of a priori probability P-alpha beta between the theory and the molecular dynamics (MD) simulation. Our model gives satisfactory agreement with experiment on the mean-square unperturbed end-to-end distance, the mean-square dipole moment and its temperature dependence, and the molar cyclization equilibrium constants for dimethylsiloxane oligomers. This new rotational isomeric state approach can be widely applied to other chains; such as -CH2-C[(CH2)(m)H](2)- and -O-Si[(CH2)(m)H](2) for arbitrary m.

Composite structural modeling and tensile mechanical behavior of graphene reinforced metal matrix composites

Owing to its distinguished mechanical stiffness and strength, graphene has become an ideal reinforcing material in kinds of composite materials. In this work, the graphene（reduced graphene oxide） reinforced aluminum（Al）matrix composites were fabricated by flaky powder metallurgy. Tensile tests of pure Al matrix and graphene/Al composites with bioinspired layered structures are conducted.By means of an independently developed Python-based structural modeling program, three-dimensional microscopic structural models of graphene/Al composites can be established, in which the size, shape, orientation, location and content of graphene can be reconstructed in line with the actual graphene/Al composite structures. Elastoplastic mechanical properties, damaged materials behaviors, grapheneAl interfacial behaviors and reasonable boundary conditions are introduced and applied to perform the simulations. Based on the experimental and numerical tensile behaviors of graphene/Al composites, the effects of graphene morphology,graphene-Al interface, composite configuration and failure behavior within the tensile mechanical deformations of graphene/Al composites can be revealed and indicated, respectively.From the analysis above, a good understanding can be brought to light for the deformation mechanism of graphene/Al composites.

Chiroptical properties of artemisinin and artemether investigated using time-dependent density functional theory

Chiroptical properties including electronic circular dichroism（ECD） and optical rotatory dispersion（ORD） of artemisinin and artemether have been fully studied using quantum-chemical calculation based on time-dependent density functional theory.Both theoretical ECD and ORD of these two compounds were in good match with the experimental data.ECD spectrum of artemether could be totally attributed to the peroxide group,and that of artemisinin was an overlay of contribution from δ-lactone and peroxide moieties,which leading to a positive maximum at 260 nm.Our results showed that peroxide group could produce a broad ECD band in the far-UV region originated from electron transitions of HOMO →LUMO,HOMO-1 →LUMO and HOMO-2 →LUMO in the case of artemether.This work provided a theoretical interpretation of the ECD behavior of peroxide bond.